The invention relates to a forming station for chip or fiber panels.
In the production of chip and fiber panels, flowable materials such as chips or fibers provided with binder agents are discharged out of a metering or dosing hopper and delivered by a conveyor or transport apparatus to a spreading head, by means of a forming station. A material mat or fleece of the chips or fibers is spread by the spreading head onto a continuously running forming belt, and this material mat or fleece is then pressed to form a panel in a pressing station. Since panels of various different thicknesses and various different material compositions are usually to be spread with such forming stations, the spreading of the material fleece must be exactly regulatable, in order to produce a homogeneous panel quality that remains as constant as possible.
Such a spreading station is previously known from the company prospectus xe2x80x9cForming Stationxe2x80x9d, SP 0208, issue of March 1985, by the company Carl Schenck AG in Darmstadt. This forming station consists of a metering or dosing hopper, out of which the glued chips are discharged by means of a floor belt and discharge rollers over the entire width. This constant chip flow is delivered by means of a conveyor or transport apparatus to the spreading head, which spreads the chips into a material mat or fleece on a continuously running forming belt arranged thereunder. In this context, the entire process sequence of the material flow is automatically regulatable. For this purpose, a surface area weight or weight-per-unit-area scale is arranged behind the spreading head, and determines the actual weight per unit area (kg/m2) and compares it with a prescribed rated weight per unit area value. The determined regulation deviation is then regulated out by appropriate control of the transport speed of the discharge rollers and of the floor belt in the dosing hopper. By this regulation of the transport speed of the discharge rollers and of the floor belt, it is not taken into account, that the discharge material of the chips or fibers is strongly dependent on its flowability, its specific weight or density, and also its Ad degree of gluing. A regulation of such type is therefore relatively inexact, and mostly only regulatable in longer cycles, whereby in the intermediate time, considerable quantities of deviating fiber mat or fleece will be spread, which will lead to panels of reduced quality.
It is therefore the object of the invention, to improve the regulation of the material flow so that the mass of the spread material mat or fleece is very constant.
This object has been achieved by the invention in a forming station comprising at least one dosing hopper, out of which a total material flow of flowable materials comprising wood chins or fibers provided with a binder agent, is discharged onto a conveying apparatus and delivered by the conveying apparatus to at least one spreading apparatus, which spreads the total material flow of the chips or fibers in a controllable quantity to form a fleece thereof onto a forming belt, wherein the conveying apparatus comprises a dosing belt scale which is arranged between the dosing hopper and the spreading apparatus, and by means of which an actual conveying rate of the total material flow on the dosing belt scale is determined as a mass per unit time, and further comprising a regulating unit, which regulates the conveying of the total material flow by the dosing belt scale based on the determined actual conveying rate (kg/s) and in consideration of a prescribed nominal conveying rate (kg/s). Further details and advantageous example embodiments of the invention are recited in the dependent claims.
With the invention, a high regulation quality of the spread-out material fleece is advantageously also achievable, because the prescribed weight per unit area of the material to be spread out is regulated directly by means of the detected weight of the delivered material. Thereby, a very stable and rapid stabilizing or regulating-out of any regulation deviations can be advantageously achieved, because a deviation is detected in the delivered material directly before or in front of the spreading-out process, and is then immediately readjusted to be regulated in terms of weight.